Oxidative stability of Commercial Omega-3 Supplements – A comparative study of three products available on the Swedish market

Abstract

Introduction: Omega-3 fatty acid supplements are widely used as an alternative to eating oily fish. However the polyunsaturated oils they contain are highly susceptible to oxidation, which can lead to rancidity and possibly decreased quality of the supplement.
Background: Despite the convenience of omega-3 supplementation, there is limited independent information on the oxidative quality of products available on the Swedish market and how everyday storage conditions affect their stability over time.
Aim(s): The aim of this study was to compare initial oxidation status of three commercial omega-3 supplements (Elixir Pharma, Biosalma and Puori) and evaluate how different storage conditions affect the peroxide value (PV), anisidine value (AV) and the total oxidation value (TOTOX) over four weeks.
Methods: Oxidation parameters were measured in triplicates using established titration and spectrophotometric methods from European Pharmacopoeia. Capsules were stored under four conditions: fridge (5°C), room temperature in darkness, room temperature with sunlight exposure, and elevated temperature (37°C).
Results: All products, except for Puori, showed acceptable initial oxidation levels. Biosalma showed highest stability with minimal changes across conditions. Elixir Pharma exhibited moderate increases in PV and TOTOX, under warmth and sunlight. Puori displayed significantly elevated AV, likely attributed to presence of aldehydic compounds from the flavoring agents, but presented lowest PV value of all. Most values remained within GOED recommended limits (PV ≤ 5 milliequivalents peroxide oxygen per kilogram oil (meq O₂/kg), AV ≤ 20, TOTOX ≤ 26), none exceeded drastically.
Conclusion: The tested commercial omega-3 supplements are generally of acceptable oxidative quality upon purchase and when stored properly, with refrigeration being most effective.

Keywords: omega-3, fish oil, oxidative stability, peroxide value, anisidine value, TOTOX

Popular Abstract

Fishy Business: Are omega-3 capsules as fresh as they promise?
Omega-3 fatty acids are important for the body, especially the brain and heart. They are mainly found in oily fish, but taking it in the form of a supplement might be easier than eating salmon twice a week, as Livsmedelsverket suggests. Fish oil, however, whether in food or supplements, is delicate and spoils (oxidizes) easily, especially when exposed to air, light or heat. This causes the oil to break down, which can smell fishy and could affect its quality.
In this degree project, I investigated how fresh three popular omega-3 supplements available on the Swedish market really are, and how different storage conditions affect their quality over four weeks. The three tested products were: Elixir Pharma Omega-3 Forte, Biosalma Omega-3 Forte 70%, and Puori O3 Fish Oil, a more expensive option with lemon flavor.
For the experiment, I measured two oxidation markers using standard laboratory methods: peroxide value (PV), indicating early-stage spoilage, and anisidine value (AV), indicating later-stage spoilage. PV and AV were combined into a total oxidation value TOTOX. Capsules were stored for four weeks under four conditions: fridge (5°C), room temperature in the dark, room temperature with sunlight, and an elevated temperature in GC-oven (37°C).
The results showed all three products started with acceptable or good oxidation levels when first opened, except Puroi, which had a high AV because of its natural lemon flavoring, not poor oil quality. Puori, nevermind the high AV, had the lowest early oxidation value, PV. Elixir Pharma showed moderate increases, especially when kept warm or in sunlight. Biosalma was a clear winner, for staying very stable with almost no increase in oxidation regardless of storage.
Overall, the omega-3 supplements in Sweden are generally of good quality at purchase, but storage at home matters. Keeping them in the fridge is the best way to maintain freshness. Warm temperatures clearly speeds up spoilage.

• author: Dudko, Julia
• supervisor: Peter Spégel
• organization: Department of Chemistry
• course: KEMK10 20261
• year: 2026
• type: M2 - Bachelor Degree
• subject: Chemistry
• keywords: omega-3, fish oil, oxidative stability, peroxide value, anisidine value, TOTOX, analytical chemistry
• language: English
• id: 9235969
• date added to LUP: 2026-06-12 13:31:18
• date last changed: 2026-06-12 13:31:18